Try searching your computer for the file. Go to the start menu, look for the item that says "search" (on a mac, click on the magnifying glass at the top of the screen) and search for the name you saved it as. If it's anywhere on your computer, you'll see it there.
And if you don't find it that way, search .sb and it'll find all the Scratch projects on your computer. It's also possible that it got deleted somehow.
Off-topic: hmn, you posted 18 seconds after midnight
That happened to me too, and I absolutely couldnt find it, even with a complete computer search! I jad an 'error' warning bc of it. File too big? Make 2 copies of important copies and u cant lose them!
i figured it out! my remixed projects go into some weird "secret" folder. I decided that when i save my projects, i should save to scratch projects before i close the window
1. 8-10 month necro
2. nice job, i had problems like that.
Had to bot up in safe cause i accidentally saved in Sys32